Sound emitting device



April 26, 1932. 1.. A. KING ET AL 1,855,837

SOUND EMITTING DEVICE Filed Nov. 1, 1929 2 Sheets-Sheet -1 Z Wmum \Zy WAZZ zm 42% Al April 26, 1932. L. A. KING ET AL SOUND EMITTING DEVICE Filed Novyl, 1929 2 Sheets-Sheet 2 devices, andmore fersadapted to be employed 'Wltll radio-re- Patented Apr. 26, 193.2

UNITED :sTATEs imrrenr ioJF'FIcE TO OPERADIQ' MANUFACTURING 00.; OF ILLINOIS LAURENCE -A.' KING AND IIARODIIDY HISHOTWELL," OF'ST. CHARLES, ILLINOIS, ASSIGNORS ST. CHARLES; ILLINOIS,"A CORPORATION OF SOUND EMIT'I'ING"DEVICE Application filed November .I The invention: relates: to sound emitting particularly to loud speakcelving sets, phonograph pick-up devices, sound picture apparatus, andthe like.

A particular object of the invention is to i provide devices of; the kind described which are particularly adapted for theatre, or outdoor Work, and combines desirable. features of an; air-column speaker with thoseof an electro-dynamic speaker.

'Fundamental frequencieszzas low .as 50 to 70 cycles are reproduced in air-column speakers having reproducing units which comprise metal diaphragms, and-:becauseof the 'power required to drive the higher frequencies throughthe lIlg"2L1I.,COll.l1IlIl, the lowire- I quencies are predominantin' the sound emitted from the sound passage.

One advantage of an-a-ir-column loudspeaker is that the sound is concentrated and directed inaspeciiic direction, and because of this carrying power the various frequencies that are reproducednare substantially equal.

'5 Another advantage isthat all of the energy comes out of the mouth of the horn in the di ection desired and no energy issuesfrom the back of the speaker 'to cause disagreeable acoustical efi'ects or loss of energy.

Frequencies 'frc1n'50 up to 5000 or 6000 cycles are readily reproduced by an electro-dynamic cone type speaker which has been properly designed and isprovidedwith a well designed ba-iile, but the characteristics of a speaker of this type are such that at a distance 50 feet away from the speaker the reproduction begins to thin out and only certain frequencies reach one under normal intensity. Another disadvantage of this speaker is that equal amounts of energy are projected from the back and fr nt of the diaphragm and the energy issuing from the back of the diaphragm tends to produce undesirable acoustical effects which are particularly noticeable in theatre Work.

'1, 1929. Serial No. 404,091.

Our improved speaker combin'estheadvantages of the air-column speaker with those of: the electrodynamic speaker in such manner that they combine for the advantages of each type. The improved speaker is of such proportions that it maybe readilypositioned in. back of a soundscreen.

Many other objects and advantages will appear as this. description; progresses, refer- :ence being-had to the accompanying drawings;wherein ."Figure'l is 'aifront elevationof aloud speaker which" embodies the invention Fig. 2. is a rear. elevation of the improved speaker;

:Eig. .3' is: an enlargedsection taken on line '.33 ofzFig'll;

Fig. 4 isian enlarged section taken on line of'Fig. l;

1]? i-g. 5 isra perspective of one of a plurality .of'clip devices for holding a screen'in position over the'mouth of the speaker; and

Fig. 6 is a front elevation of one of a plu- 'rality of'arcuate members-which co-operate with the clip devices to'hold the screen in position over the mouth of the speaker.

Referring to the drawings, thereference character 10 designates, generally, a speaker of the electro-dynamictype,'th-e speaker 10 being provided with a diaphragm 11 which comprises a conical portion 13. The conical portion 13 is aperture-d at its apex and secured to the conical portion at the aperture therein is a sleeve 15 which carries a coil or windinglG adapted tobe connected to the output circuit of a radio-receiving set,'ph0- nograph pick-up, sound picture apparatus, or the like. The winding 16 is hereinafter referred toasthe voice coil.

At its larger end, the conical portion 13 of the diaphragm 1.1 is provided with an annular flange 18 which. projects into an annular space provided between felt rings 19 and 20 carried by cardboard rings 21 and 22, respectively, the felt and cardboard rings being mounted in a metallic ring 24 which is preferably secured to a supporting ring 26 by screws 27, or the equivalent.

The voice coil 16 is concentrically disposed in an annular magnetic gap 30 formed between a central pole piece 31 and an annular pole piece 32, the annular pole piece 32 being rigidly secured to a cup-shaped magnet member 34 which carries the central pole piece 31. Disposed around the pole piece 31 is a winding 36 which is connected by conductors 37 and 38 to any suitable source of direct current. Preferably, formed integral with the cup-shaped magnet member 34 are a plurality of radially extending arms 40 which carry the supporting ring 26' and are preferably formed integral therewith.

The opening in the front end of the speaker 10 is preferably closed by a screen 42 carried by a metallic ring 43 secured to the supporting ring 26.

As is well known to those skilled in the art, fluctuations in the current flowing in the voice coil 16 react with the annular mag netic field 30 and cause the voice coil and the diaphragm 11 to vibrate so that the fluctuations of the current in the voice coil are translated into sound.

The electro-dynamic speaker 10 is preferably mounted in the central opening of an annular member 46 which is preferably molded from plastic material and co-operates with a dished member 47 to provide an annular sound passage 48, the construction being such that the annular sound passage 48 has an annular mouth 49 encircling the annular member 46. The dished member 47 is also preferably formed from plastic material. The inner surfaces 50 and 51 of the annular member 46 and the dished member 47 respectively, are preferably formed in such manner that a section through the speaker on any diameter thereof appears to show two sound passages extending from the back or outer surface of the diaphragm 11 to diametrically disposed portions of the mouth 49. The construction is such that the surfaces 50 and 51 are more or less exponential, the actual curves of these surfaces being determined, to some extent, by the size of the speaker. It will be noted that the dished member 47 is preferably provided with a central projection 55 which has its outer ends disposed in close proximity to the apertured apex of the conical portion 13. Obviously energy projected from the back surface of the diaphragm 11 is projected through all parts of the sound passage 48 and issues from the mouth thereof. Energy projected from the front surface of the diaphragm 11 is projected in the same direction through the screen 42.

Disposed around the edge of the dished member 47 are metallic rings 57 and 58, and

FY disposed around the outer edge of the annular member 46 are metallic rings 59 and 60. The rings 57, 58, 59 and 60 reinforce the dished member 47 and the annular member 46, respectively, and co-operate with a plurality of bolts 61 to support the annular member 46 concentrically with respect to the dished member 47. Thus, it will be noted that the bolts 61 are provided with a plurality of nuts 65 which may be manipulated to secure the members 46 and 47 in adjusted positions with respect to each other.

Additional means for supporting the annular member 46 concentrically with respect to the dished member 47 comprise a plurality of bolts 68 which project through the walls of the members 46 and 47 and are provided with nuts 69 which may be manipulated to secure the members 46 and 47 in adjusted positions with respect to each other.

The mouth 49 is preferably covered by a plurality of arcuate screens 70 which are held in place by means including a plurality of arcuate members 72, each of Which is pro 'vided with a plurality of screw-threaded holes 73 (see Fig. 6). The outer edges of the arcuate screens 70 are preferably clamped between the arcuate members 72 and the front edge of the dished member 47, and the arcuate members 72 are secured in place by clip members 75 having slotted ends 76 adapted to be clamped between some of the nuts 65 and the ring 57. Screws 78, or the equivalent, project through the clip members 75 and are screw-threaded into the screw-threaded holes 7 3 provided in the arcuate members 72.

Similar means is provided for clamping the inner edges of the arcuate screens 70 to the annular member 46. Thus, we preferably provide a plurality of arcuate bars 80 which resemble the arcuate members 72, but

are smaller in size. The inner edges of the screens are clamped between the arcuate bars 80 and the peripheral edge of the annular member 46. The arcuate bars 80 are held in place by clip members 81 which are preferably identical in construction with the clip members 75 and are held in place by having portions thereof clamped between the ring 60 and some of the nuts 65 provided upon the bolts 61. Screws 84, or the equivalent, se- I cure the ends of the arcuate members 80 to the clip members 81.

As best shown in Fig. 1, we also prefer to provide a plurality of metallic straps 85 at the joint between the several screens 70,

the ends of the straps 85 being preferably clamped between the clips 75 and 81 and the arcuate members 72 and 81.

Any suitable means may be provided for supporting the improved speaker, but we prefer to employ a base which is designated generally by the reference characters 87 and is preferably fabricated from a plurality of metallic straps or bars.

As best shown in Figs. 1 and 3, a U-shaped 7 i connection with bar 88 is positioned below the front end of the speaker, and as best shown in Figs. 2 and 8, a flat supporting bar 89 is provided at the back end of the speaker. The ends of a substantially xi-shaped bar 90 are secured to the ends of the bar 89 and the central portion of the i -shaped bar 90 is secured to an L- shaped bar 93 by a bracket 9e (see Fig. The L-shaped bar 93 is also secured to the bars 88 and 89 and to one of the bolts 68.

The conductors 3i and 38 leading from the terminals of the field winding 36 of the magnetizing structure, which comprises the pole pieces 31 and 32, preferably pass through an aperture 95 provided in the supporting ring 26 and having their outer ends connected to terminals (not shown) provided in a junction box 98 carried by the annular member i6. A cable 100 having suitable electrical conductors therein connects the terminals not shown) in the junction box 98 with a power pack 101 carried by the base 87. The power pack 101 is provided if the field winding 36 is to be energized from a source of alternating current, and preferably comprises a step-down transformer and a rectifier. ()f course, if the field winding is to be energised from a comm rcial source of direct current, it is not necessary to provide the power pack. It will be noted that the cable 100 passes through apertures 108 and 10% provided in the annular member 46 and the dis. meml or 47, respectively.

The means for securing the electro-dynamic speaker 10 to the annular member 46 preferably comprises a metallic ring 110 mm bedded in a front edge of the annular member 4-6 and anchored to the annular mem- ,ber by a plurality of bracket members 111, the bracket members 111 being referably embedded in the annular member during the molding operation. The aforementioned screws 27 are utilized to secure the supporting ring 26 to the ring 110.

It will be noted that the improved speaker shown in the drawings is relatively thin from the front surface to the back surface thereof. This construction enables it to be employed with advantage behind a sound screen when the space in back of the sound screen is rather small. Another advantage of the speakers embodying the present invention is that they have tremendous carrying power for air port or outdoor work, as they have large wave front.

The electro-dynamic speaker 10 is preferably of approximately the same size as electrodynamic speakers now in general use in radio-receiving sets, and therefore it is, in itself, enough to be employed as a loud speaker in a relati' -rcly large room. The diameter of the dished member l? is proportionately large, and we have obtained satisfactory results v. ith speakers in. which the dished members a? are from 5 to 51/ feet in diameter. Of course, the Wavefront is substantially the same diameter.

The annular member 16. functions both as a battle between the front and back surfaces of the diaphragm and as a part of the means for amplifying the sound projected from the back surface of the diaphragm.

A feature of the invention is the provision of an electro-dynamic speaker in which the magnetizing structure is disposed substantially within the conical diaphragm. By positioning the magnetizing structure adjacent the inner or concave side of the conical diaphragm, the construction of our improved speaker is simplified as the energy projected from the back surface of the diaphragm is readily delivered into the sound passage d8.

While We have shown and described certain embodiments of our invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construc tion and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the append-ed claims, in which it is our intention to claim all novelty inherent in our invention as broadly as possible, in view of the prior art.

What we regard as new, and desire to secure by Letters Patent is:

1. A device of the kind described comprising a sound passage having an inlet end and terminating at the other end in an annular mouth, and a sound reproducing unit disposed at said inlet end, said sound reproducing device comprisin a conical diaphragm having its outer or back surface arranged to project energy into said sound passage and having its inner or front surface arranged to project energy in substantially the same direction as said mouth.

2. A device of the kind described comprising an annular sound passage having an inlet end, and a sound reproducing unit disposed at said inlet end and comprising a diaphragm having one side arranged to project energy into said sound passage and having its other side arranged to project energy directly away from the device.

8. A device of the kind described comprising an annular member, a dished member forming a sound passage with said annular member and provided with a central lug projeeting toward said annular member, and a reproducing unit carried by said annular member and provided with a conical diaphragm, the back or outer side of the diaphragm being arranged to project energy into said sound passage and the front or inner side of said diaphragm being arranged to project energy directly away from said de- Vice.

at. A device of the kind described comprislng an annular member, a dished member, means for holding said members in spaced relation to provide a sound passage having an annular mouth, a sound reproducing unit communicating With said sound passage, a

plurality of arcuate screens for said mouth,

and means for securing said screens to said annular and dished members.

5. A device of the kind described comprising a sound passage having an inlet end and terminating at the other end in an annular mouth, and a sound reproducing unit disposed at said inlet end, said sound reproducing unit comprising a diaphragm having one surface arranged to project sound into said sound passage and having its other surface arranged to project sound in substantially 15 the same direction as said mouth.

6. A device of the kind described comprising a dished member, an annular member disposed in said dished member and cooperating therewith to form an annular sound pas- 29 sage, and a sound reproducing device carried by said annular member, said sound reproducing device having a diaphragm of which one side projects sound into said annular sound passage and of Which the other 25 side projects sound directly into the air in front of the device.

7. A device of the kind described comprising a dished member, an annular member disposed Within said member, said dished mem- 39 ber and said annular member co-operating to form a sound passage whereof the central aperture of said annular member is the inlet, and a sound reproducing unit disposed at said inlet, and provided with a diaphragm, one

side of said diaphragm being adapted to project sound into said sound passage and the other side thereof being adapted to project sound into the air in front of said dished member.

19 In testimony whereof, We hereunto set our hands this 30th day of September, 1929.

LAURENCE A. KING. HAROLD H. SHO'UVELL 

